ON THE SYNTHESIS OF ALKALINE-EARTH DIHALIDES AND THE STRUCTURES OF CA3BR2CBN AND SR3CL2CBN

The reaction of alkaline-earth carbonates with ammonium chloride or bromide yields alkaline-earth dihalides at relatively low temperatures (300-degrees-C). Ca3Br2CBN and Sr3Cl2CBN were synthesized in sealed niobium containers at 950-degrees-C from the metal, its dihalide, boron nitride and graphite. The crystal structure of Sr3Cl2CBN was refined from single crystal data. Sr3Cl2CBN crystallizes isotypic with Ca3Cl2CBN in the orthorhombic space group Pnma (No. 62) with a = 1448.4(2) pm b = 405.46(5) pm, c = 1170.0(1) pm. The lattice constants of Ca3Br2CBN and Sr3C12CBN were determined by orthorhombic indexing of the powder patterns (Ca3Br2CBN: a = 1444.3(2) pm, b = 390.64(6) pm, c = 1139.2(2) pm; Sr3Cl2CBN: a = 1444.0(4) pm, b = 405.27(8) pm, c = 1167.8(2) pm). There was no success in preparing homologues with Barium.